How can you tell if a guy genuinely likes you or if he just wants sex?

Anonymous
I recently met this guy at work who’s really nice and I kinda like him. But so many girls like him and I think he does flirt with a lot of people so I keep my distance from him. He told me that I was very pretty and I think maybe I make him nervous because he laughs a lot when talking to me at things that weren’t even that funny but I don't know. He also asked my friend if I had a boyfriend but I feel like he probably just wants sex.
How can you tell if a guy genuinely likes you or if he just wants sex?
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